Competition of rapeseed proteins and oleosomes for the air-water interface and its effect on the foaming properties of protein-oleosome mixtures

Abstract

There is an increasing interest to apply oleosomes (plant oil storage organelles) as natural oil droplets in food systems. Lipids are usually known to be detrimental for protein-stabilised foams due to the weakening of interactions between adsorbed proteins, or by forming oil bridges between two protein surfaces. Both mechanisms can lead to film rupture, and thereby destabilise protein-stabilised foams. Little is known about the influence of oleosomes on protein-stabilised interfaces and foams. Therefore, these properties were studied for rapeseed protein–oleosome mixtures at various protein concentrations and ratios. At 0.1 and 0.2% (w/w) protein content, oleosomes were found to co-adsorb with proteins at the interface, followed by rupture of oleosomes and release of triacylglycerols and phospholipids. This led to weaker in-plane interactions between adsorbed proteins. As a result, the foamability and foam stability of protein-oleosome systems were substantially lower compared to systems made with pure proteins. At 0.5 and 1.0% (w/w) protein content, the rapeseed proteins were found to dominate the interfacial properties. The proteins formed a dense solid-like layer at such high concentrations, which prevented the oleosomes from co-adsorbing at the interface. Also, in foam systems at high protein concentrations, the proteins seemed to outcompete the oleosomes for the interface, leading to higher foam stability. Here, we have demonstrated that the detrimental influence of oleosomes on protein-stabilised interfaces and foams can be controlled by varying the amount of oleosomes and rapeseed proteins in the mixture, which is a promising outcome to further utilise oleosomes in aerated food systems.